Dennis harbigan and joel whitney



@with faire gat/tent ffice.'

DENNIS HARRIGAN AN D JOEL WHITNEY, OF WIN CHESTER, MASSACHUSETTS.

I Letters .Patent No. 78,095, dated January 7, 1868.

vIl\l[l:"lt0Vllltlffihl T IN WORM FOR GEARS.

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Be it known that we, DENNIS HARRIGAN and Jenn WHITNEY, both of Winchester, in the State of Massaehusetts, have invented an improved form of Worm for Gears; and We do hereby declare the following is 'a full andcxact description thereof, reference being had to the accompanying drawings, and to the letters ot. refer- In these'drawings, the letter A, Figure l, represents a toothed wheel, of a common iorm, its face concave to adapt it to the reception of a. Worm. There is nothing new in the form of this wheel. In the driving endless the screw, through the middle of said threads, these lines will be found to be parallel; while lines drawn through the middle ot' the teeth of the driven wheel, which .engages these threads, from the-'circumference inward, are convergent, and, in fact, radii of the wheel oi which they arelthe teeth. Again, a line drawn along the outer edge of the threads ot' the ordinary worm, (line my, 'g. 2,) parallel to the axis, is a straight line, x/vhile a line drawn along the outer edge oft-he teeth of the driven wheel (a: .fz/, g. 1) is an are, ot' whichv the axis of the wheel is the centre. Hence it follows that but one tooth of the driven wheel is completely engaged at a time of thc lines through the screw-threads being parallel, if' drawn in the same pla'ne from axis to circumference of driving-screw, these teeth are so cut that these lin'es will converge, and, if continued, would meet at -a point distant from the hase or root of the threads equal to the radius of the driven wheel. Thus, it' lines be drawn ot' the driven wheel, and is soon destroyed. In our invention, however, all these defects are avoided. Instead point, C, distant from the roots of the threads -equal to the radius of the wheel A., and are, 'in fact, runde by a tool, which, instead of' travelling along the face of the screw a distance equal to therlength thereof, vibrates on an axiswhose radius is equal to that of the driven wheel. V While, also, the threads of the common worm or screw are turned upon a cylinder, in our invention they may be turned upon a hody whose surfaces from end toend of'rthe screw, in a direction parallel with the axis, are concave, the radiusof the concavity beingl equal to that ot the driven wheel; and as the height of allfthe threads from root to summit is the same, it follows that What we' claimhthen, as our invention, is`

An endlessscre/w or Worm, with its threads so termed las to have their general direction from root to summit 'such that, 1`t` prolonged, they would meet at a point distant from the roots of the threads equal to the radiiof the wheel they are intended to drive. u

Weclaim, also, the forming of these threads upon a body whose bounding-lines, in a direction parallel with the axis of the worm, are concave, the radius of the concavity being equal, or nearly so, to the radins ot the wheel to be driven.

DENNIS 'HARRIGAN,

JOEL WHITNEY Witnesses:

WILLIAM PERKINS TYLER, F. D. STEDMAN 

